New Heat-Reduced Magnetic Solder Could Revolutionize Chip Design

A new heat-reduced soldering technique using magnets may lead to some revolutionary changes in the way chips are manufactured. Details are scant since the inventor seems to be playing it close to the vest for now in hopes of attracting chipmaker interest. "The result is a tin-silver alloy that contains a dispersion of iron particles tens of micrometers in diameter. When a magnetic field is applied to the solders, two things happen. First, the iron particles heat up, locally melting the solder. This localized heating, which works on the same principle as inductive stoves, remains completely contained, keeping the surrounding area cool. And second, the iron particles line up with the direction of the magnetic field, squeezing and pushing the liquid in that direction. This alignment is retained when the solder solidifies, and the well-ordered particles provide mechanical reinforcement that's greater than that afforded by a regular dispersion of particles."

Accidental reflow?

[pavon]

From the article:

A new type of solder can be melted and shaped in three dimensions under the force of a weak magnetic field

How weak are we talking about here? I wouldn't want my chips to become desoldered just because they were exposed to an electromagnetic field. The article didn't mention any thing about that.

JB Weld

[macraig]

JB Weld contains so much iron particulate in suspension that it responds to a magnetic field. If it weren't for the fact that the particles are so much larger and get drawn out of suspension and toward the magnet, it might be possible to speed-cure the stuff with this same trick.

Re:Accidental reflow?

[moteyalpha]

What about -intentional- reflow. It would be useless for Mil Spec certainly and I would guess that war walking could take on a new level of meaning. It would be interesting if they used multipurpose dies that could be connected and recycled to a new configuration. Oh yes, liquid metal terminator brains. Mmm brains.

Re:What about the RF characteristics?

[Sponge Bath]

I don't think the particles are spheres. The article says tens of microns in diameter, but also says the particles align to the magnetic field and never mentions spheres. I would guess the particles are cylindrical. Also pure iron has a permeability comparable to some ferrites.

Isn't that how we make cold joints

[millwoodtwo]

In soldering 101 I learned that if you put hot solder on cold metal, the solder doesn't really wet the joint, and you will get early or immediate failure of conductivity. You can even accidentally create a diode. So why will this work?

Re:Accidental reflow?

[X0563511]

Hmm. How would the solder bond to connections though? From what I'm getting from this, the solder (and just the solder) would heat up. Basically you'd get a blob of molten solder refusing to bond to anything because of surface tension?

(100% guaranteed cold solder joints, basically)

You could pre-tin the connections, but then wouldn't the solder just remelt (while the metal plating remains cold) and "ball" off?

Re:Wait....

[Anonymous Coward]

Without a circuit there can be no magnetically induced current.

Wrong. You forget about capacitance. A small amount of current can be induced in any conductive material merely by moving the magnetic field around it. This current will be absorbed by capacitance (only to be re-emitted shortly thereafter). When you have bottlenecks in the material, like are found in any IC, the current may be enough to cause damage.